JPH03241782A - Electrostrictive effect element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of an electrostrictive element.

[Conventional technology]

An electrostrictive element is a transducer that converts electrical energy into mechanical energy by utilizing the electrostrictive effect of a solid state. Specifically, electrodes such as metal films are formed on opposing surfaces of a solid that has a large electrostrictive effect, and the strain in the solid that occurs when a potential difference is applied between the electrodes is utilized. Since the strain that occurs in the direction parallel to the electric field (longitudinal effect strain) is generally larger than the strain that occurs in the perpendicular direction (transverse effect strain), energy conversion efficiency is higher when using the former.This longitudinal effect, which has high energy conversion efficiency, In an electrostrictive effect element that utilizes a Increasing the size requires a large and expensive power source, which also increases the risk of handling.

In order to improve such defects, the
) has been proposed as a multilayer chip capacitor type structure. In the figure, an internal electrode 2 is placed inside the electrostrictive material 1.
electrodes a and 2b are formed at regular intervals, and every other electrode is interconnected with external electrodes 3a and 3b. internal electrode 2a,
The spacing between 2b is several 1 using normal multilayer chip capacitor technology.
The thickness can be set to about 0 μm. If this structure is adopted, the distance between the electrodes becomes narrower, so an electrostrictive effect element using the longitudinal effect that can be driven at a low voltage can be realized.

By the way, as is clear from the projection view of FIG. 4(b) viewed from the stacking direction, in this structure, the overlapping area of the internal electrodes (
The central rectangular portion) is small compared to the cross-sectional area of the element. Therefore, basically, the overlapping part of the internal electrodes deforms in response to the electric field, but the other parts do not. Therefore, when a high voltage is applied and a large strain is generated, some parts deform and are difficult to deform. There is a drawback that a large stress concentration occurs at the boundary between the parts and the element is mechanically destroyed.

In order to improve these drawbacks of conventional elements, grooves ( There is a structure that forms a slit (hereinafter referred to as a slit) (Japanese Patent Application Laid-Open No. 58-196077). In other words, in a cross section perpendicular to the stacking direction of the device, by removing a part of the periphery that is not involved in deformation of the device, stress concentration is alleviated, thereby increasing the lifespan until mechanical failure occurs under repeated voltage pulse application. In addition, the displacement of the element can be increased.

[Problem to be solved by the invention]

The problems of the conventional electrostrictive effect element described above will be explained with reference to the drawings.

FIG. 6(a) is a vertical cross-sectional view of a conventional electrostrictive effect element.
Figures (b) and (c) are diagrams in which the slit shape 5 and the internal electrodes 2a, 2b, 2c, and 2d are projected onto a plane perpendicular to the stacking direction of the element.

two internal electrodes 2c located across the slit 6;
2d are connected to different external electrodes 3a and 3b, respectively. Therefore, when a voltage is applied between the external type ftl1!3a and 3b, an electric field is generated between the internal electrodes 2C and 2d.

The distribution of electric lines of force at this time is shown as shown in FIG. In an electrostrictive effect element, the amount of displacement increases as the electric field strength increases, but as shown in FIG. If a high voltage is applied to extract the material, dielectric breakdown is likely to occur at that part. As described above, the conventional structure has the disadvantage that a large amount of displacement cannot be obtained because the applied voltage must be kept low so as not to cause dielectric breakdown.

The purpose of the present invention is to eliminate such drawbacks and connect the two internal electrodes that sandwich the slit to the same external electrode, thereby avoiding concentration of electric field at the tip of the slit and preventing dielectric breakdown from occurring. An object of the present invention is to provide an electrostrictive effect element capable of extracting a displacement amount.

[Means to solve the problem]

In the tank bottom of the present invention, materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated, and these internal electrodes are connected to one of two external electrodes, and on the side surface parallel to the lamination direction of these elements. , in an electrostrictive effect element in which grooves are formed at one or more places parallel to the electrode surface of the internal electrode at predetermined intervals, two internal electrodes sandwiching the multi-grooves are formed on the same external electrode; It is characterized by being connected.

Moreover, in the present invention. The distance between the two internal electrodes sandwiching each groove may be narrower than the distance between the other internal electrodes.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a), (b), and (c) are longitudinal cross-sectional views of an electrostrictive element showing the structure of an embodiment of the present invention, and the slit shape 5 and internal electrodes 2a to 2h are shown in the stacking direction of the element. The internal electrodes 2e and 2f located across the slit 6 are both connected to the external electrode 3a, and similarly the internal electrodes 2g and 2h are both connected to the external electrode 3.
connected to b. Therefore, even if a voltage is applied to the external electrodes 3a and 3b, no electric field is generated in the layer where the slit 6 is located.

In this example, the cross section of the electrostrictive element is 4×4IllI
ll, internal electrodes 2a, 2e, 2f and 2b, 2g.

The part that overlaps with 2h is marked 3x3, and the slit shape 5 is 3x
It was set as 3■. The element height is 10 mm, the spacing between the slits 6 is about 0.5++++n, the spacing between the internal electrodes to which voltage is applied is about 100 μm, and the spacing between the internal electrodes 2e and 2f and between 2g and 2h, that is, the spacing between the slits 6 The thickness of one layer was approximately 200 μm. Internal electrodes 2a, 2b, 2
A total of 80 sheets were formed for e to 2h. The device of this example is
Since no voltage is applied to the layer with the slit 6, no displacement occurs; therefore, in this embodiment, there are 60 layers (hereinafter referred to as functional layers) in which displacement occurs.

As a specific example of this example, a lead zirconate titanate material exhibiting an electrostrictive effect was used for investigation. An organic solvent, a binder, and a plasticizer were added to the pre-fired powder of this material, and a green sheet with a thickness of about 130 μm was produced using a doctor blade method. After drying this green sheet, a predetermined number of sheets of internal electrode paste containing silver-palladium alloy powder as a main component and slit pore forming material paste containing carbon as a main component are screen printed on it. They were cut into shapes, laminated, and bonded under heat. This was fired at 1100°C. The slits 6 are formed by scattering the pore-forming material during this temperature rise. After this firing, the Ag paste for external electrodes was baked, and then lead wires for voltage application were connected.

The electrostrictive effect element according to this embodiment and the conventional i-structured electrostrictive effect element that differs only in the arrangement of internal electrodes (79 functional layers)
After 20 pieces of each were polarized at 150 VDC for 1 minute, changes in displacement were investigated when voltage was applied at a boost rate of 100 VDC/min. The results are shown in the graph of FIG. In an element with a conventional structure, 28
In contrast, dielectric breakdown occurred at 014O-50V, whereas dielectric breakdown did not occur even at 700V in the element according to the present invention. As a result, a larger amount of displacement was obtained compared to elements with conventional structures.

FIG. 3 is a longitudinal sectional view of an electrostrictive element according to a second embodiment of the present invention. Internal electrode 2 located across slit 6
Since no voltage is applied between e and 2f or between internal electrodes 2g and 2h, no dielectric breakdown occurs even if the distance between the electrodes in this area is shortened.

In this example, the distance between the internal electrodes was 50 μm. Further, the thickness of the slit 6 itself is approximately 5 μm. The element height is 10
IIIa, the distance between internal electrodes to which voltage is applied is approximately 100μ
m, both have the same dimensions as in the first embodiment. A total of 11 internal electrodes 2a, 2b, 2e to 2h were formed.

The number of functional layers in the device of this example is 84. Other dimensions were consistent with the first example. The characteristic diagram in FIG. 2 shows the results of investigating changes in displacement when voltage was applied under the same conditions as in the first embodiment.

In this example, an element having a higher voltage-displacement efficiency than the conventional structural element was obtained, and when a voltage was applied to 20 elements of this example, no dielectric breakdown occurred at 700 .mu.m.

〔Effect of the invention〕

As explained above, according to the present invention, two internal electrodes sandwiching a slit are connected to the same external electrode, thereby preventing dielectric breakdown when high voltage is applied. Therefore, there is an effect that an electrostrictive effect element having a structure that has a high dielectric breakdown voltage and can extract a larger amount of displacement can be obtained.

[Brief explanation of drawings]

FIG. 1(a) is a vertical cross-sectional view of an electrostrictive effect element according to an embodiment of the present invention, and FIGS. 1(b) and (C) are slit shapes 5 of FIG.
FIG. 2 is a characteristic diagram showing the change in displacement when voltage is applied, and FIG. 3 is a diagram showing the second embodiment of the present invention. A vertical cross-sectional view of FIG. 4(a). (b) is a vertical cross-sectional view of an element with a conventional multilayer chip capacitor structure and a projected view of its internal electrode 2, FIG. 5 is a cross-sectional view of a conventional element, and FIG. 6 (a). C) is a longitudinal cross-sectional view of an element with a conventional structure and a projected view of its slit shape 5 and internal electrodes 2a, 2b, and FIG. 7 is a schematic diagram showing the distribution of electric lines of force in the element of the conventional example. 1... Electrostrictive material, 2a to 2h... Internal electrode, 3a. 3b... External electrode, 4... Lead wire, 5... Slit shape, 6... Slit.

Claims (2)

[Claims] 1. Materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated, and these internal electrodes are connected to either of the two external electrodes, and the electrode surface of the internal electrode is placed on the side surface parallel to the lamination direction of these elements. An electrostrictive effect element comprising one or more grooves formed at a predetermined interval in parallel with the grooves, characterized in that two internal electrodes sandwiching each groove are connected to the same external electrode. An electrostrictive effect element. 2. 2. The electrostrictive effect element according to claim 1, wherein the distance between the two internal electrodes sandwiching each groove is narrower than the distance between the other internal electrodes.